# Regulation (EU) 2018/1861 of the European Parliament and of the Council of 28 November 2018 on the establishment, operation and use of the Schengen Information System (SIS) in the field of border checks, and amending the Convention implementing the Schengen Agreement, and amending and repealing Regulation (EC) No 1987/2006, Article 21: Proportionality

Extent: E+W+S+N.I.

1. Before entering an alert and when extending the period of validity of an alert, Member States shall determine whether the case is adequate, relevant and important enough to warrant an alert in SIS.
2. Where the decision to refuse entry and stay referred to in point (a) of Article 24(1) is related to a terrorist offence, the case shall be considered adequate, relevant and important enough to warrant an alert in SIS. For public or national security reasons, Member States may exceptionally refrain from entering an alert when it is likely to obstruct official or legal inquiries, investigations or procedures.

---
Source: https://www.legislation.gov.uk/eur/2018/1861/article/21 (the official version)
Page: https://openlegislation.uk/eu-regulation-2018-1861/article-21
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.